Keaton studied acting at Santa Ana College in California and at the Neighborhood Playhouse in New York. She appeared in summer stock in the mid-1960s and in 1968 understudied the lead in the Broadway rock musical Hair. She had the lead role in Woody Allen’s Broadway play Play It Again, Sam (1969), which she later reprised for the 1972 film version. Keaton made her motion-picture debut in Lovers and Other Strangers (1970); her character, a young naïf divorcing her husband because his hair no longer smells like raisins, established a comic persona that would sustain her early career.

Though she acted in Francis Ford Coppola’s gangster dramas—The Godfather (1972) and The Godfather, Part II (1974)—she appeared mostly in Allen’s comedies during the 1970s, including Sleeper (1973), Love and Death (1975), Interiors (1978), and Manhattan (1979).

Keaton’s watershed year was 1977: in two films she not only established herself as a star but succeeded in both reinventing her screen persona and capitalizing on her established one. Allen’s Annie Hall—which won Academy Awards for best picture, actress, and director—is probably the role for which she is best known, appearing as the archetypal Keaton “kook.” Based on the real-life relationship between Allen and Keaton, the film chronicles Annie’s transformation from shy awkwardness to mature confidence. In many ways it was an autobiographical statement for Keaton, who made a dramatic turn the same year in Richard Brooks’s dark, violent Looking for Mr. Goodbar. She continued in that vein as journalist Louise Bryant in Warren Beatty’s Reds (1981), which earned her another Oscar nomination.

Keaton found continued success in such diverse films as Shoot the Moon (1982), The Little Drummer Girl (1984), Crimes of the Heart (1986), and the popular Baby Boom (1987). She reunited with Allen for a cameo in Radio Days (1987) and a leading role in Manhattan Murder Mystery (1993). During the 1990s she appeared in several films with broad appeal, such as The Godfather, Part III (1990), the romantic farce Father of the Bride (1991), and the melodrama Marvin’s Room (1996). In the early 21st century Keaton starred in a number of light hearted lighthearted comedies, including Something’s Gotta Give (2003), opposite Jack Nicholson; The Family Stone (2005); Because I Said So (2007); and Morning Glory (2010), in which she and Harrison Ford portrayed TV anchors with clashing personalities. Keaton also directed several pictures.